1. Field of the Invention
The present invention generally relates to treatment of ventricular tachycardia, and more particularly, relates to percutaneous treatment of ventricular tachyarchia using laser energy.
2. Description of the Prior Art
Ventricular tachycardia is a disease of the heart in which the heart's normal rhythmic contraction is altered, thus effecting left ventricular function. The condition is often described as a heart beat which is too fast, although the disease is far more complex. In many patients the orderly contractions of the heart are not present because various portions of the myocardium do not contract and relax in proper synchronism with the rest of the heart.
Currently, the most common treatment for tachycardia is through the use of various drugs. Some drugs reduce the irritability of the offending myocardial tissue, whereas other drugs may slow the response time of all myocardial tissue. In either case the treatment is administered systemically resulting in various side effects.
A second technique now gaining some popularity is surgical intervention. Initially, surgery was performed only in those circumstances which were totally refractory to drug therapy, however, surgical intervention is now more popular. The technique involves electrophysiological mapping of the myocardium. Foci of the tachycardia are located and surgically excised. The major disadvantage of this procedure is the cost and risk associated with open chest cardiac surgery. A description of the surgical procedure may be found in "Endocardial Excision: A new Surgical Technique for the Treatment of Recurrent Ventricular Tachycardia", by Mark E. Josephson, M.D., et al, Circulation, Volume 60, Number 7, 1979.
A first variation on surgical excision involves cryosurgery. In this technique, the diseased myocardial tissue is destroyed by freezing. See for example "The Successful Cryosurgical Treatment of Paroxyal Ventricle Tachycardia", Chest, Volume 75, at page 612, 1979. Other variations involve the use of DC shock and radiofrequency energy.
Perhaps the most promising technique similar to surgical excision is with the use of laser energy. Such a technique is described in "Neodymium: YAG Lase photocoagulation: A Successful New Map-Guided Technique for the Intraoperative Ablation of Ventricular Tachycardia", by Robert H. Svenson, M.D., et al., Circulation, Volume 76, Number 6, Dec. 1987. This technique attempts to photocoagulate rather than ablate the diseased tissue. In this way the mechanical integrity of the myocardium is preserved. However, because the method of Svenson, et al. is intraoperative, the major problem with surgical excision (i.e., need to perform a thorocotomy) is not overcome by this technique. The difficulty that remains is the cost and trauma associated with this procedure.